Spreading Dynamics and the Residence Time of Ellipsoidal Drops on a Solid Surface.

Controlling bouncing drops on solid surfaces has gained significant attention because of the benefit of low residence time in anti-icing and self-cleaning strategies. Given that the drop shape at the moment of impact is classically assumed to be spherical, the residence time on a flat surface is bounded by a theoretical Rayleigh limit. In this study, we investigated the impact dynamics of oblate and prolate ellipsoidal drops to demonstrate the concept of modifying the residence time by shaping like raindrops. Experimental and numerical studies show that the initial shape plays a vital role in an increase or reduction in bounce speed of the drop, which is explained by scaling the maximum spreading time. The hydrodynamic features of ellipsoidal drops are analyzed by quantifying the temporal variations in diameters, heights, velocity fields, momenta, and energy dissipation. We believe that the ellipsoidal drop impact can provide an efficient pathway for controlling the residence time in practical applications.